An ostensibly peaceful protest this weekend exploded into fatal riots, killing at least 156 people and injuring more than 1,000 in Urumqi, the capital of China's western, oil-rich region of Xinjiang. The original Uighur protesters demanded a government investigation of two deaths at a remote factory, the result of an earlier clash between Uighurs and Han Chinese, The New York Times reported. Spurred by Sunday's riots, Han Chinese protested on Tuesday morning, calling the government "far too soft" in its measures against Uighur leaders, The Times of London reported.

Although many have characterized these riots as China's most serious unrest since Tiananmen Square, such violence is not new to the region, the BBC reports. Low-grade hostility simmers continually between the two ethnic groups. "Uighurs make up about half of the 20 million people in Xinjiang but are a minority in Urumqi, where Han Chinese dominate," according to The New York Times.

The Council on Foreign Relations (CFR) reports that in the 1990s, separatist groups in Xinjiang coordinated frequent assaults on the Chinese government. One of these groups, the East Turkestan Islamic Movement (ETIM), has been declared a terrorist organization by the United Nations Security Council, while China claims the group has ties to al-Qaeda.

Although violence ebbed after the agitation of the 1990s, a new series of deadly attacks marked the days leading up to the 2008 Beijing Olympics. The Chinese government blamed the attacks on "two ethnic Uighur separatists," Edward Wong wrote for The New York Times. But Wong went on to report doubts about Uighur responsibility and the official Chinese account.

According to the CFR, many experts believe that "China is exaggerating the danger posed by Uighur terrorists" as a justification for repressive security measures. "The Chinese government has increased repression in the Xinjiang Uighur Autonomous Region (XUAR) since 2001, building off campaigns started in the 1990s to squelch political viewpoints and expressions of ethnic identity deemed threatening to state power," according to the 2007 annual report of the Congressional-Executive Commission on China (CECC).

After the Qing Dynasty crumbled in 1912, Xinjiang achieved a level of autonomy, the CFR reports. After brief episodes of independence in the 1930s and 1940s, at one point with the support of the Soviet Union, Xinjiang fell under the Chinese Communist Party's rule in 1949. In 1955, the region officially became "an 'autonomous region' of the People's Republic of China."

Many Uighurs, according to the CFR, characterize China's actions as colonization and remain "nostalgic" for their earlier spurts of independence. Such accounts directly defy official Chinese insistence that Xinjiang, which currently comprises one sixth of China's land, has been an "inseparable part of the unitary multi-ethnic Chinese nation" since the Western Han Dynasty.

The Chinese government has launched numerous initiatives to strengthen the bonds between Xinjiang and the rest of China. Of the 20 million people who live in Xinjiang, 45 percent are Uighurs. Their ethnic affiliation with surrounding countries, including Kazakhstan, Kyrgyzstan and Tajikistan, inflames government fears of Uighur rebellion, which in turn spur Chinese diplomatic relations with its neighbors, according to the CRF.

The ruling Han Chinese, the overall ethnic majority of China, comprise only 40 percent of the region. This minority has grown dramatically from 5 percent in the 1940s, reports the CFR, due to job opportunities that "have lured a steady stream of migrant workers to the region, many of whom are ethnically Han."

The rapid influx of Han Chinese, Al Jazeera reports, has been psychologically devastating for the Uighurs, who perceive Han rule as a threat to their livelihoods, their religion and their cultural survival. Although Xinjiang is rich in oil and prosperous, it suffers from great inequality, with a wage gap that favors the Han and higher rates of incarceration among Uighurs, according to the CECC report.

The Human Rights Watch has further disclosed a "multi-tiered system of surveillance, control, and suppression of religious activity aimed at Xinjiang's Uighurs." Such accusations have led human rights groups to classify Xinjiang as China's "other Tibet," Al Jazeera reports. The CFR suggests that the Chinese positioning of the Uighurs as al Qaeda-linked terrorists might have lessened international interest in the accusations of rights abuses against them.

As in previous situations, Chinese officials shut down communications services, imposed curfews and made widespread arrests. Echoing their implication of the Dalai Lama in recent Tibetan violence, the government also blamed a foreign exile, Rebiya Kadeer, for Uighur unrest, The New York Times reported. Kadeer, who lives in Washington, is president of the World Uighur Congress.

As The New York Times reports, though, the Chinese have learned from last year's Tibetan violence that not all repressive tactics work. In Tibet, they instituted a complete media blackout, censoring both local reports and foreign media. This time, they have announced casualties, allowed foreign journalists limited access and broadcast their own videos of the violence, mainly showing Han victims.

"For Twitter or the Internet, when they see too many factors they cannot completely control, they shut down and block," Xiao Qiang, a professor at the University of California, Berkeley, told The New York Times. "But for foreign journalists, they feel that as long as they can keep those people under control, it may serve better the government's purpose."

Four Uighurs were in the news in June as part of the debate surrounding plans to close Guantanamo Bay prison. After seven years of detention in Cuba, they were cleared by the United States for release, but China has declared them "terrorists" and wants to put them on trial. In order to avoid handing the Uighurs over to China or releasing them in the U.S., the U.S. government sent the detainees to Bermuda. The U.S. had previously arranged for 13 other Uighurs from Guantanamo to live in Palau.